Just wondering if anyone could point me to any info on engine oil seals, ideally a list of all the seals there are that could need replacing?
My mk1 (1.6) has been mysteriously losing oil for a while now - maybe about 4 litres since the new year. I’m pretty sure it’s not burning oil, as no smoke from exhaust, but neither are there any visible leaks - in the past few months I’ve noticed maybe 3 small, slightly oily spots on the garage floor (usually mixed with water after it rains), but that’s it.
Have also had various seals replaced recently - CAS O-ring, crankshaft front seal, cam cover seal - head gasket replaced about a year ago.
Autolink looked it over a few months back and said they couldn’t find any obvious leaks, though they did suggest it could be the rear oil seal (the one which can only be accessed by removing clutch) - can anyone remind me of the official name of this seal, and are there any others I should investigate while I’m at it? Especially any that would not produce an obvious leak (or maybe only leak while driving along?)
Have checked FAQ, and googled for list of oil seals - no luck, so any advice much appreciated!
If your car has been examined by Autolink and they found nothing obvious I would tend to think that oil may be passing seals because of crankcase pressure. Check the breather valve for correct operation and breather hoses for any obstruction.
Thanks Simon, that sounds like the one I’m on about! Incidentally, autolink advised me to leave it alone as it would be expensive to get at what with removing the clutch - plus there was no sign of oil mess around there when they had the car in the air, and the clutch isn’t slipping, so there was no real evidence the seal was bad.
However as it’s the only seal that wasn’t directly inspected, and as the car’s still losing a lot of oil with no other explanation offering itself, I’d started to presume it must be this rear seal - until I saw Geoff’s post…
I have to admit that I have no idea what crankcase pressure is, or what/where the breather hoses are! However, this is a good thing, in so far as it means there is another possible explanation in addition to the only two I’ve seen on any other thread about oil loss (ie bad seals or burning oil). Will do some research on crankcase pressure, thanks for info!
Hi, try running the engine, pop the oil filler cap off for A couple of seconds and just put your hand over the top, you should feel A slight blowing, this is crankcase pressure but if it is excessive then I agree with Geoff. Wouldn’t hurt to take his advice anyway as it won’t do any harm. If you have any way of getting underneath the car if the rear crankkshaft oil seal has gone it will probably be leaking where the bell housing bolts to the block
There is indeed the way to test if the rear oil seal is leaking (significantly) - loosen one or two bolts at the bottom of the bell housing and see if oil comes out.
I’ve curently no way of raising the car in the air, but it’s good to know how this can be checked without actually removing clutch - will ask the next mechanic I take it to to have a look. It’s very useful to get all this info even if I can’t do the work myself, as mechanics don’t seem to always volunteer to do these sort of investigations unless you specifically suggest it…
Will also try the test with the oil filler cap, thanks!
Breather valve on drivers side of engine between cam cover and inlet manifold. Tube should be clear and valve should allow air to pass one way only. Breather hose on passenger side of engine between the cam cover and the air intake duct across the front of the engine, remove it and check it is clear.
OK checked all these - both breather pipes seem clear, valve works - you can feel air coming from the oil filler hole, but doesn’t seem excessive (about equal to if you made a small “O” with your mouth and breathed out medium-hard, but not full strength - if that makes sense…)
Only thing I noticed was the passenger-side breather pipe is split at the end where it attaches to the cam cover, but only about a cm split, so I think it still seals up fine when attached. Will of course order a new one just to be sure.
Thanks for the detailed walk-through btw, I now know my way around a few more parts of the engine than I did before, even if I haven’t quite solved the mystery oil loss yet!
One other quick question - if crankcase pressure was the cause of the oil loss, would I expect a visible leak, and if so would it come from anywhere specific?
A split breather should be fine…it just means the crank will vent into your engine bay (and slowly cover everything with a light mist of oil. Ideally everything should go into the manifold and out the exhaust.
Seeing as it’s not dropping oil on the floor, there is nowhere it can be going except out the exhaust or into the bell housing from the rear oil seal. But…it won’t take long to fill up and ruin your clutch if it’s disappearing quickly.
You say you had the head gasket replaced a year ago…does that by any chance coincide with starting to lose oil??
A split breather hose will result in air being drawn into the air intake duct downstream of the airflow meter. This will upset the PCM and interfere with engine managment. Modern engines to not vent to atmosphere. Even the fuel tank has to vent via a charcoal canister under controlled conditions to the inlet manifold. To return, the oil is disappearing somewhere, either past seal(s) gasket(s), past piston rings down the valve guides or simply a leak from the filter etc. All I am thinking is that if Autolink could not find anything obvious a compression test may would verify the condition of the bores etc. Then it is a process of elimination. Do you have any figures as to how much oil is being lost, say per 1,000 miles?
The head gasket was replaced about 2 months after I bought the car while replacing a deformed exhaust valve - hard to say when oil loss started, though I get the feeling it’s been gradually losing more oil over time. Certainly sounds like the bell housing is the most likely place it’s going, but clutch seems fine. Is there any way I can check for oil in the bell housing without going under the car?
I wonder if this split breather hose could explain another mystery with this car - occasionally on startup (usually if the engine is still warm) the idle speed will droop judderingly low for 30 seconds or so before settling at wherever I’ve set the base-idle. Have ordered new hose, so should know soon enough!
As for figures, I’ve done about 3000 miles since the new year, and used about 4 litres of oil since then. This is a fairly rough estimate, but even if it’s less oil than that, would still be a lot more than normal! Am using semi-synthetic 10W-40 oil btw.
Looks like I’m running out of things I can check myself (especially as I’ve no way of going under car) so a trip to a mechanic is probably inevitable to solve this oil loss problem. Will definitely ask for a compression test on the cylinders - (low compression figures would suggest the oil was being burnt, right?)
Thanks again for all the info - let me know if there’s anything else I can check myself before I take it to a mechanic (or anything else I should ask them to check!)